Materials

Pulsed Plasma Lubricator (PPL) Technology for the In Situ Replenishment of Dry Lubricants in Extreme Environments

Applications include mechanisms that are not easily serviced in the field, including those used in deep sea or arctic oil drilling. NASA missions employing mobility systems and other moving mechanical assemblies for application on Mars, the Moon, and in deep space depend on the reliable operation of these assemblies and their tribological components. Wet lubricants are sometimes used in space applications, but in order to avoid solidification, they often require active heating due to the extreme cold temperatures that are encountered. Dry lubricants, such as molybdenum disulfide (MoS2), are more commonly chosen for space mechanisms because they are not subject to the low-temperature limitations of wet lubricants while also providing superior lubricating properties. A major drawback of dry lubricants is low wear resistance that eventually leads to failure of the assembly as the lubricant is removed.

Posted in: Materials, Briefs, TSP

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Long-Life, Hydrophilic, Antimicrobial Coating for Condensing Heat Exchangers

New coating uses a modified structure intended to inhibit diffusion, slow hydrolysis, and lengthen the coating life. Future manned spacecraft and lunar or Mars outposts will need a condensing heat exchanger (CHX) to control humidity in the cabin atmosphere. Condensing surfaces must be hydrophilic to control condensate flow and ensure efficient operation in zero gravity, and biocidal to prevent growth of microbes and formation of biofilms on condensing surfaces. Coatings must be extremely stable, adhere to the condensing surface, and maintain hydro philic and biocidal properties for many years.

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Opposed Pad Gecko Adhesive Gripper for On-Off Omnidirectional Anchoring/Gripping in Orbit

Applications include satellite servicing and inspection of inflatable habitats. The idea of turning the stickiness of a material on and off is not an intuitive concept, yet this is exactly how geckos run up walls at speeds greater than 1 m/s and cling to ceilings made of glass. Transitioning this capability to spacecraft would constitute a major breakthrough because it would provide improved capabilities for multiple mission types.

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Complex Geometry Multi-Use Coatings for Abrasion Prevention, Wear Resistance, and Lunar Dust Removal

Two coatings are required to remove/repel lunar dust particles from the mechanism or surface that needs protection. One coating must be a conductor, and one must be a dielectric. Tungsten carbide (WC) and aluminum oxide (Al2O3) were found to be best suited as the conductor and dielectric, respectively.

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Improving Material Property Measurement Using Multi- Camera Digital Image Correlation

The automotive industry faces growing pressure for more efficient vehicles. This pressure comes from many sources including government regulations, decreasing natural resources, and consumer demand. As the pressure begins to rise, automakers have a growing need for better fuel, more efficient energy-generating processes, and lighter vehicles. In an effort to reduce the weight of their vehicles, automakers have shown an increasing interest in using aluminum, provided it can withstand the same deformations as steel.

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Mechanistic-Based Multiaxial- Stochastic-Strength Model for Transversely- Isotropic Brittle Materials

The methodology is applicable to a wide variety of graphite, coatings, and composite materials. A methodology has been developed and the software written to predict the probability of failure of transversely isotropic (a type of anisotropy) materials under generalized thermomechanical loading. This methodology is mechanistic in that it is based on the physical characteristics of brittle fracture, and morphological in that it considers the size, shape, and orientation distribution of strength controlling defects or flaws. On that basis, it can also account for a material’s failure modes and direction of damage initiation from loading. It is capable of predicting an anisotropic material’s probability of failure under transient and cyclic loading. This innovation can be applied to materials such as graphite, coatings, or the individual brittle constituents of composite materials.

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Bulk Metallic Glasses and Matrix Composites as Spacecraft Shielding

These materials offer combinations of high hardness, low melting temperature, low density, and formability like a plastic. Spacecraft shielding is defined as the outer layer of a satellite or spacecraft that protects it against micrometeorite and orbital debris (MMOD), radiation damage, and re-entry temperatures. There are several problems with the design and implementation of shields, particularly in the area of MMOD shielding. Spacecraft and satellites need to have the lowest possible mass due to the enormous cost per pound of putting them into orbit or deep space. However, low Earth orbit (LEO) is currently littered (and increasingly so) with orbital debris, primarily remnants of rocket upper stages, satellites, and pieces of spacecraft that have broken away or have collided with other objects. The major threat is that this debris is traveling at 8 to 18 km/s, and any piece larger than a few centimeters has the kinetic energy to potentially become a “spacecraft killer.” Large debris is tracked with radar, but the smaller debris (below a centimeter or so) is too small to track and must be mitigated by shields in the event of a collision. The International Space Station, for example, employs over 500 different shield designs into its outer skin, which are designed to protect a variety of vital components.

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